Stabilization of Outer Domain of gp120 from HIV-1 Subtype C for Vaccine Immunogen Design

The outer domain of gp120 is a relatively stable domain compared to the inner domain and bridging sheet at the CD4-binding site for the HIV-1 primary receptor. Therefore, the outer domain has been considered as an immunogen candidate for vaccine design. In this report, we focused on the VRC01 antibody binding epitope in the outer domain and evaluated the effects of introducing two disulfides to further stabilize the outer domain structure where the antibody binds for the purpose of generating a more effective immunogen. Our experimental data based on neutralization activities against HIV-1 of anti-sera produced from immunized guinea pigs demonstrated that this stabilized outer domain-based immunogen significantly enhances the specific immune response when compared to its wild-type outer domain counterpart. These findings strongly suggest that this structure-based designed epitope is effective in eliciting specific neutralizing antibodies against diverse HIV-1strains, including subtype C.